My family bought this TV new 17 years ago. We never had any trouble with it until a year ago when it made a loud spark and the picture went blank momentarily. It did the same thing again several months later. Recently it's developed a second problem where the picture develops a fog with about twenty inclined horizontal line segments. The lines start and end about 1 inch from the left and right edge of the picture, respectively. They do not move vertically. The fog looks the same as what you would see if the G2 (screen) voltage were set too high. The picture geometry and focus look normal. The fog problem never starts until at least 10 seconds after the TV is turned on. Then it usually does occurs, although it sometimes disappears for a while only to return again. The sparking problem has increased, but it has only occurred when the fog wasn't there.
I've tested several voltages in the system, including B+, the regulated voltage to the Horizontal Output Transistor, the heater/filament, G1, G2 (screen), and the CRT anode. All voltages, except G1, drop about 5% during the fog. G1, which is about 32v normally, will jump as high as
140v during the fog. The brighter the fog the higher it goes.
I tried disconnecting the power to G1. The fog problem became worse and the voltage on the G1 pin continued to spike. I then reconnected G1 and disconnected G2. I was certain that the picture wouldn't appear. I was wrong. The picture came up and then the fog reappeared. The instant I touched the terminal pin for G2 with my test lead to test the voltage the picture went almost completely black.
I've read Sam's guide (thanks for the wealth of info) on TV repair which lead me to the conclusion that the CRT is shorting. The guide mentions discharging a capacitor across the shorted components but I'm unsure exactly what's shorting or how many farads to use. I'm hoping one of you experts out there can advise me on what to do next. Is there any hope? Should I pull the plug on this beloved family member for good?
Many thanks, Scott